1. Field of the invention
The invention relates to an improved system and method for rehabilitation of a sectionalized portion of a structurally damaged or leaking gravity flow system, service line, joint, crown failure and the bridging of offset pipe joints by the installation of a cured-in-place thermosetting resin impregnated structural liner.
2. Description of related art
Ruptures, cracks and holes often occur in underground conduits such as sanitary sewer lines, storm sewer pipes, and other gravity flow systems and service lines. Repairing these ruptured conduits, from within, is far less expensive and less dangerous than excavating and replacing the damaged sections. One such repair method is to introduce into the conduit a polyester-fiberglass or other structural composite liner impregnated with a thermosetting resin. The liner is wrapped around and secured to an inflatable bladder carrier which is positioned at the rupture and inflated, forcing the repair liner against the inside wall of the conduit. The impregnated composite liner adheres to the damaged inner surface of the conduit and hardens. After completion of the curing process, the bladder is deflated and removed from the conduit. Known related art include U.S. Pat. Nos. 4,995,761 and 5,049,003 to Barton, U.S. Pat. No. 5,628,345 to Fisco, U.S. Pat. No. 5,322,653 to Muller, U.S. Pat. No. 3,202,562 to Lang, et al., U.S. Pat. No. 3,261,374 to Anderson, et al., U.S. Pat. No. 4,776,370 to Long , U.S. Pat. No. 4,880,035 to Vetter, U.S. Pat. No. 4,950,446 to Kinumoto, et al., U.S. Pat. Nos. 4,985,196 and 5,091,137 to LeDoux, et al., U.S. Pat. No. 5,199,463 to Lippiatt, U.S. Pat. No. 5,203,377 to Harrington, U.S. Pat. Nos. 5,213,727 and 5,346,658 to Gargiulo, U.S. Pat. No. 5,265,648 to Lyon, and U.S. Pat. No. 5,501,248 to Kiest, et al.
A major recurring problem not remedied by known related art occurs when the resin impregnated liner slides, twists, buckles up or otherwise moves with respect to the inflated bladder carrier while being pulled through the conduit to the section of the conduit to be repaired. The liner might typically encounter a protruding pipe or other foreign object and get caught on the object. The liner will either slide partly or fully off the carrier, tear, or will fold back upon itself. Sometimes friction with a course surfaced conduit is enough to cause slippage. Consequently, when the carrier appears to be in the correct position the liner may not be in the proper position. If the problem is left undetected and the liner is not removed prior to inflating the bladder carrier, the cured repair liner may miss the damaged area. Further, the damaged area may be so close to the outside edge of the repair liner that the integrity of the repair is questionable. In addition, the repair liner may cure and harden in a distorted configuration within the conduit thus necessitating the need to remove the defectively installed repair liner, a costly and difficult process. The major problem can be traced back to improper or inadequate attachment of the repair liner to the bladder carrier, and the concomitant difficulty in releasing the repair liner from the bladder carrier. Previous prior related art methods and devices have not been able to overcome this problem.
Previous related art methods of holding the repair liner in place focus on holding the leading edge of the repair liner in place during movement within the conduit to the repair location; wrapping a break-away string around the repair liner, the break-away string breaking upon inflation of the bladder; or using rollers to separate the repair liner from the internal wall surface of the conduit. These methods do not remedy the problems encountered as described above, as the repair liner can nevertheless become distorted or move either during movement of the carrier or during the bladder inflation process or the break-away string may prematurely break during the movement of the carrier within the conduit.
Another problem encountered in the prior related art concerns the composite structural repair liner construction. Prior related art utilizes repair liners constructed with fiber-reinforced material such as a fiberglass mat attached to a polyester, foam, or felt mat. The capacity of such dual layered repair liners to absorb and hold sufficient amounts of thermosetting resin, thus ensuring a uniform bond with the internal surface of the conduit being repaired and ensuring a smooth internal finish after cocuring and removal of the carrier, is limited.